Camshaft phaser

ABSTRACT

A camshaft phaser includes an input member; an output member defining an advance chamber and a retard chamber with the input member; a supply passage; a vent passage; and a valve spool within the output member which is moveable between a first and second position. The first position prevents communication between the advance chamber and the vent passage, prevents communication between the retard chamber and the vent passage, and allows oil to flow from one of the advance chamber and the retard chamber to the other of the advance chamber and the retard chamber. The second position provides communication between the vent passage and one of the advance chamber and the retard chamber, prevents communication between the vent passage and the other of the advance chamber and the retard chamber, and provides communication between the supply passage and the other of the advance chamber and the retard chamber.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims the benefit of U.S. provisional patent application Ser. No. 62/552,985 filed on Aug. 31, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD OF INVENTION

The present invention relates to a camshaft phaser for varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine; more particularly to such a camshaft phaser which is a vane-type camshaft phaser; even more particularly to a vane-type camshaft phaser which is switchable from using only torque reversals of the camshaft to actuate the camshaft phaser to using at least pressurized oil from an external oil source to actuate the camshaft phaser.

BACKGROUND OF INVENTION

A typical vane-type camshaft phaser for changing the phase relationship between a crankshaft and a camshaft of an internal combustion engine generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to one of the advance and retard chambers and vacated from the other of the advance and retard chambers by a phasing oil control valve in order to rotate the rotor within the stator and thereby change the phase relationship between the camshaft and the crankshaft. One such camshaft phaser is described in U.S. Pat. No. 8,534,246 to Lichti et al., the disclosure of which is incorporated herein by reference in its entirety and hereinafter referred to as Lichti et al.

While the camshaft phaser of Lichti et al. may be effective, the camshaft phaser may be parasitic on the lubrication system of the internal combustion engine which also supplies the oil for rotating the rotor relative to the stator, thereby requiring increased capacity of an oil pump of the internal combustion engine which adds load to the internal combustion engine. In an effort to reduce the parasitic nature of camshaft phasers, so-called cam torque actuated camshaft phasers have also been developed. In a cam torque actuated camshaft phaser, oil is moved directly from the advance chambers to the retard chambers or directly from the retard chambers to the advance chambers based on torque reversals imparted on the camshaft from intake and exhaust valves of the internal combustion engine. The torque reversals are predictable and cyclical in nature and alternate from tending to urge the rotor in the advance direction to tending to urge the rotor in the retard direction. The effects of the torque reversals on oil flow are known to be controlled by a valve spool positioned by a solenoid actuator. Accordingly, in order to advance the camshaft phaser, the valve spool is positioned by the solenoid actuator to create a passage with a first check valve therein which allows torque reversals to transfer oil from the advance chambers to the retard chambers while preventing torque reversals from transferring oil from the retard chambers to the advance chambers. Conversely, in order to retard the camshaft phaser, the valve spool is positioned by the solenoid actuator to create a passage with a second check valve therein which allows torque reversals to transfer oil from the retard chambers to the advance chambers while preventing torque reversals from transferring oil from the advance chambers to the retard chambers. However, requiring two check valves adds cost and complexity to the system. One such camshaft phaser is described in U.S. Pat. No. 7,000,580 to Smith et al., hereinafter referred to as Smith et al.

It is also known to provide a camshaft phaser which can utilize both oil pressure from an oil source external to the camshaft phaser as well as torque reversals imparted on the camshaft to actuate the camshaft phaser. However, such known camshaft phasers may be complex to implement.

What is needed is camshaft phaser which minimizes or eliminates one or more the shortcomings as set forth above.

SUMMARY OF THE INVENTION

Briefly described, a camshaft phaser is provided for use with an internal combustion engine for controllably varying the phase relationship between a crankshaft and a camshaft in the internal combustion engine. The camshaft phaser includes an input member connectable to the crankshaft of the internal combustion engine to provide a fixed ratio of rotation between the input member and the crankshaft; an output member connectable to the camshaft of the internal combustion engine and defining an advance chamber and a retard chamber with the input member; a supply passage which introduces pressurized oil into the camshaft phaser from an oil source; a vent passage which selectively discharges oil from the camshaft phaser; and a valve spool within the output member which is moveable between a first position and a second position. The first position 1) prevents fluid communication between the advance chamber and the vent passage, 2) prevents fluid communication between the retard chamber and the vent passage, 3) allows oil to flow from one of the advance chamber and the retard chamber to the other of the advance chamber and the retard chamber, and 4) prevents oil flow from the other of the advance chamber and the retard chamber to the one of the advance chamber and the retard chamber. The second position 1) provides fluid communication between the vent passage and one of the advance chamber and the retard chamber, 2) prevents fluid communication between the vent passage and the other of the advance chamber and the retard chamber, and 3) provides fluid communication between the supply passage and the other of the advance chamber and the retard chamber.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be further described with reference to the accompanying drawings in which:

FIG. 1 is an exploded isometric view of a camshaft phaser in accordance with the present invention;

FIG. 2 is a radial cross-sectional view of the camshaft phaser in accordance with the present invention;

FIG. 3 is a cross-sectional view of the camshaft phaser in accordance with the present invention taken through advance and retard passages of a rotor of the camshaft phaser;

FIG. 4 is a cross-sectional view of the camshaft phaser in accordance with the present invention taken through a lock pin of the camshaft phaser;

FIG. 5 is an enlarged portion of FIG. 4 showing a valve spool of the camshaft phaser in a default position with a lock pin engaged with a lock pin seat;

FIG. 6 is the view of FIG. 5 now shown with the valve spool in a first retard position now with the lock pin retracted from the lock pin seat;

FIG. 7 is the view of FIG. 5 now shown with the valve spool in a second retard position now with the lock pin retracted from the lock pin seat;

FIG. 8 is the view of FIG. 5 now shown with the valve spool in a hold position now with the lock in retracted from the lock pin seat;

FIG. 9 is the view of FIG. 5 now shown with the valve spool in a first advance position now with the lock pin retracted from the lock pin seat;

FIG. 10 is the view of FIG. 5 now shown with the valve spool in a second advance position now with the lock pin retracted from the lock pin seat;

FIGS. 11 and 12 are isometric views of an insert of a valve spool of the camshaft phaser in accordance with the present invention; and

FIG. 13 is an isometric cross-sectional view of the valve spool and the insert of the camshaft phaser in accordance with the present invention.

DETAILED DESCRIPTION OF INVENTION

In accordance with a preferred embodiment of this invention and referring to FIGS. 1-4, an internal combustion engine 10 is shown which includes a camshaft phaser 12. Internal combustion engine 10 also includes a camshaft 14 which is rotatable about a camshaft axis 16 based on rotational input from a crankshaft and belt (not shown) driven by a plurality of reciprocating pistons (also not shown). As camshaft 14 is rotated, it imparts valve lifting and closing motion to intake and/or exhaust valves (not shown) as is well known in the internal combustion engine art. Camshaft phaser 12 allows the timing between the crankshaft and camshaft 14 to be varied. In this way, opening and closing of the intake and/or exhaust valves can be advanced or retarded in order to achieve desired engine performance.

Camshaft phaser 12 generally includes a stator 18 which acts and an input member, a rotor 20 disposed coaxially within stator 18 which acts as an output member, a back cover 22 closing off one end of stator 18, a front cover 24 closing off the other end of stator 18, a lock pin 26, a camshaft phaser attachment bolt 28 for attaching camshaft phaser 12 to camshaft 14, and a valve spool 30. The various elements of camshaft phaser 12 will be described in greater detail in the paragraphs that follow.

Stator 18 is generally cylindrical and includes a plurality of radial chambers 31 defined by a plurality of lobes 32 extending radially inward. In the embodiment shown, there are four lobes 32 defining four radial chambers 31, however, it is to be understood that a different number of lobes 32 may be provided to define radial chambers 31 equal in quantity to the number of lobes 32. Stator 18 may also include a toothed pulley 34 formed integrally therewith or otherwise fixed thereto. Pulley 34 is configured to be driven by a belt that is driven by the crankshaft of internal combustion engine 10. Alternatively, pulley 34 may be a sprocket driven by a chain or other any other known drive member known for driving camshaft phaser 12 by the crankshaft.

Rotor 20 includes a central hub 36 with a plurality of vanes 38 extending radially outward therefrom and a rotor central through bore 40 extending axially therethrough. The number of vanes 38 is equal to the number of radial chambers 31 provided in stator 18. Rotor 20 is coaxially disposed within stator 18 such that each vane 38 divides each radial chamber 31 into advance chambers 42 and retard chambers 44. The radial tips of lobes 32 are mateable with central hub 36 in order to separate radial chambers 31 from each other. Each of the radial tips of vanes 38 may include one of a plurality of wiper seals 46 to substantially seal adjacent advance chambers 42 and retard chambers 44 from each other. While not shown, each of the radial tips of lobes 32 may also include one of a plurality of wiper seals 46.

Back cover 22 is sealingly secured, using cover bolts 48, to the axial end of stator 18 that is proximal to camshaft 14. Tightening of cover bolts 48 prevents relative rotation between back cover 22 and stator 18. A back cover seal 50, for example only, an O-ring, may be provided between back cover 22 and stator 18 in order to provide an oil-tight seal between the interface of back cover 22 and stator 18. Back cover 22 includes a back cover central bore 52 extending coaxially therethrough. The end of camshaft 14 is received coaxially within back cover central bore 52 such that camshaft 14 is allowed to rotate relative to back cover 22. In an alternative arrangement, pulley 34 may be integrally formed or otherwise attached to back cover 22 rather than stator 18.

Similarly, front cover 24 is sealingly secured, using cover bolts 48, to the axial end of stator 18 that is opposite back cover 22. A front cover seal 54, for example only, an O-ring, may be provided between front cover 24 and stator 18 in order to provide an oil-tight seal between the interface of front cover 24 and stator 18. Cover bolts 48 pass through back cover 22 and stator 18 and threadably engage front cover 24, thereby clamping stator 18 between back cover 22 and front cover 24 to prevent relative rotation between stator 18, back cover 22, and front cover 24. In this way, advance chambers 42 and retard chambers 44 are defined axially between back cover 22 and front cover 24.

Camshaft phaser 12 is attached to camshaft 14 with camshaft phaser attachment bolt 28 which extends coaxially through rotor central through bore 40 of rotor 20 and threadably engages camshaft 14, thereby by clamping rotor 20 securely to camshaft 14. In this way, relative rotation between stator 18 and rotor 20 results in a change is phase or timing between the crankshaft of internal combustion engine 10 and camshaft 14.

Oil is selectively transferred to advance chambers 42 from retard chambers 44, as result of torque applied to camshaft 14 from the valve train of internal combustion engine 10, i.e. torque reversals of camshaft 14, in order to cause relative rotation between stator 18 and rotor 20 which results in retarding the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Conversely, oil is selectively transferred to retard chambers 44 from advance chambers 42, as result of torque applied to camshaft 14 from the valve train of internal combustion engine 10, in order to cause relative rotation between stator 18 and rotor 20 which results in advancing the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Alternatively, pressurized oil can be supplied, from a source external to camshaft phaser 12, to advance chambers 42 while oil is vented out of camshaft phaser 12 from retard chambers 44 in order to cause relative rotation between stator 18 and rotor 20 which results in retarding the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Conversely, pressurized oil can be supplied, from the source external to camshaft phaser 12, to retard chambers 44 while oil is vented out of camshaft phaser 12 from advance chambers 42 in order to cause relative rotation between stator 18 and rotor 20 which results in advancing the timing of camshaft 14 relative to the crankshaft of internal combustion engine 10. Rotor advance passages 56 may be provided in rotor 20 for supplying and venting oil to and from advance chambers 42 while rotor retard passages 58 may be provided in rotor 20 for supplying and venting oil to and from retard chambers 44. Transferring oil to advance chambers 42 from retard chambers 44 and transferring oil to retard chambers 44 from advance chambers 42 as well as supplying pressurized oil to advance chambers 42 or retard chambers 44 from the external source and venting oil out of camshaft phaser 12 from advance chambers 42 or retard chambers 44 is controlled by valve spool 30 and a phasing check valve 62, as will be described in detail later, such that valve spool 30 is coaxially disposed slidably within a valve bore 64 of camshaft phaser attachment bolt 28 where valve bore 64 is centered about camshaft axis 16.

Lock pin 26 selectively prevents relative rotation between stator 18 and rotor 20 at a predetermined aligned position of rotor 20 within stator 18, which as shown, may be a full advance position, i.e. rotor 20 as far as possible within stator 18 in the advance direction of rotation. Lock pin 26 is slidably disposed within a lock pin bore 66 formed in one vane 38 of rotor 20. A lock pin seat 68 is provided in front cover 24 for selectively receiving lock pin 26 therewithin. Lock pin 26 and lock pin seat 68 are sized to substantially prevent rotation between stator 18 and rotor 20 when lock pin 26 is received within lock pin seat 68. When lock pin 26 is not desired to be seated within lock pin seat 68, pressurized oil is supplied to lock pin bore 66 through a rotor lock pin passage 72 formed in rotor 20, thereby urging lock pin 26 out of lock pin seat 68 and compressing a lock pin spring 70. Conversely, when lock pin 26 is desired to be seated within lock pin seat 68, the pressurized oil is vented from lock pin bore 66 through rotor lock pin passage 72, thereby allowing lock pin spring 70 to urge lock pin 26 toward front cover 24. In this way, lock pin 26 is seated within lock pin seat 68 by lock pin spring 70 when rotor 20 is positioned within stator 18 to allow alignment of lock pin 26 with lock pin seat 68. Supplying and venting of pressurized oil to and from lock pin 26 is controlled by valve spool 30 as will be described later.

Camshaft phaser attachment bolt 28 and valve spool 30, which act together to function as a valve, will now be described in greater detail with continued reference to FIGS. 1-4 and now with additional reference to FIGS. 5-10. Camshaft phaser attachment bolt 28 includes bolt supply passages 74 which extend radially outward from valve bore 64 to the outside surface of camshaft phaser attachment bolt 28. Bolt supply passages 74 receive pressurized oil from an oil source 76 external to camshaft phaser 12, for example, an oil pump of internal combustion engine 10, via an annular oil supply passage 78 formed radially between camshaft phaser attachment bolt 28 and a counter bore of camshaft 14 and also via radial camshaft oil passages 80 of camshaft 14. The pressurized oil from oil source 76 is used to 1) replenish oil that may leak from advance chambers 42 and retard chambers 44 in use, 2) to disengage lock pin 26 from lock pin seat 68, 3) to replenish oil that is vented from lock pin 26, and 4) supply pressurized oil to advance chambers 42 or retard chambers 44 during certain positions of valve spool 30. A filter 82 may circumferentially surround camshaft phaser attachment bolt 28 at bolt supply passages 74 in order to prevent foreign matter that may be present in the oil from reaching valve spool 30.

Camshaft phaser attachment bolt 28 also includes a bolt annular lock pin groove 84 on the outer periphery of camshaft phaser attachment bolt 28, a bolt annular lock pin groove 85 on the inner periphery of valve bore 64, and bolt lock pin passages 86 extending radially outward from bolt annular lock pin groove 85 to bolt annular lock pin groove 84. Bolt annular lock pin groove 84 is spaced axially apart from bolt supply passages 74 in a direction away from camshaft 14 and is aligned with a rotor annular lock pin groove 88 which extends radially outward from rotor central through bore 40 such that rotor lock pin passage 72 extends from rotor annular lock pin groove 88 to lock pin bore 66. In this way, fluid communication is provided between valve bore 64 and lock pin bore 66.

Camshaft phaser attachment bolt 28 also includes a bolt annular advance groove 90 on the outer periphery of camshaft phaser attachment bolt 28, bolt annular advance groove 91 on the inner periphery of valve bore 64, and bolt advance passages 92 extending radially outward from bolt annular advance groove 91 to bolt annular advance groove 90. Bolt annular advance groove 90 is spaced axially apart from bolt supply passages 74 and bolt annular lock pin groove 84 such that bolt annular lock pin groove 84 is axially between bolt supply passages 74 and bolt annular advance groove 90. Bolt annular advance groove 90 is aligned with a rotor annular advance groove 94 which extends radially outward from rotor central through bore 40 such that rotor advance passages 56 extend from rotor annular advance groove 94 to advance chambers 42. In this way, fluid communication is provided between valve bore 64 and advance chambers 42.

Camshaft phaser attachment bolt 28 also includes a bolt annular retard groove 96 on the outer periphery of camshaft phaser attachment bolt 28, a bolt annular retard groove 97 on the inner periphery of valve bore 64, and bolt retard passages 98 extending radially outward from valve bore 64 to bolt annular retard groove 96. Bolt annular retard groove 96 is spaced axially apart from bolt annular advance groove 90 such that bolt annular advance groove 90 is axially between bolt annular lock pin groove 84 and bolt annular retard groove 96. Bolt annular retard groove 96 is aligned with a rotor annular retard groove 100 which extends radially outward from rotor central through bore 40 such that rotor retard passages 58 extend from rotor annular retard groove 100 to retard chambers 44. In this way, fluid communication is provided between valve bore 64 and retard chambers 44.

Valve spool 30 is moved axially within valve bore 64 of camshaft phaser attachment bolt 28 by an actuator 102 and a valve spring 104 to achieve desired operational states of camshaft phaser 12 by opening and closing bolt supply passages 74, bolt lock pin passages 86, bolt advance passages 92, and bolt retard passages 98 as will now be described. Valve spool 30 includes a valve spool bore 106 extending axially thereinto from the end of valve spool 30 that is proximal to camshaft 14. An insert 108 is disposed within valve spool bore 106 such that insert 108 defines a phasing volume 110 and a venting volume 112 such that phasing volume 110 is substantially fluidly segregated from venting volume 112, i.e. phasing volume 110 does not communicate with venting volume 112. Phasing check valve 62 is captured between insert 108 and valve spool bore 106 such that phasing check valve 62 is grounded to insert 108. By way of non-limiting example only, insert 108 may be net-formed by plastic injection molding and may be easily inserted within valve spool bore 106 from the end of valve spool bore 106 that is proximal to valve spring 104 prior to valve spool 30 being inserted into valve bore 64 of camshaft phaser attachment bolt 28. In this way, phasing volume 110 and venting volume 112 are easily and economically formed.

Valve spool 30 also includes a supply land 114 which is sized to fit within valve bore 64 in a close sliding relationship such that oil is substantially prevented from passing between the interface between supply land 114 and valve bore 64 while allowing valve spool 30 to be displaced axially within valve bore 64 substantially uninhibited.

Valve spool 30 also includes a spool annular supply groove 116 that is axially adjacent to supply land 114. A spool supply passage 118 extends radially inward from spool annular supply groove 116 to phasing volume 110 within valve spool bore 106. A supply check valve 120 is captured between insert 108 and valve spool bore 106 within phasing volume 110 such that supply check valve 120 is grounded to insert 108 in order to allow oil to enter phasing volume 110 from spool supply passage 118 while substantially preventing oil from exiting phasing volume 110 to spool supply passage 118.

Valve spool 30 also includes a lock pin land 122 that is axially adjacent to spool annular supply groove 116. Lock pin land 122 is sized to fit within valve bore 64 in a close sliding relationship such that oil is substantially prevented from passing between the interface between lock pin land 122 and valve bore 64 while allowing valve spool 30 to be displaced axially within valve bore 64 substantially uninhibited. Lock pin land 122 is axially divided by a spool annular lock pin groove 124 such that a spool lock pin passage 126 extends radially inward from spool annular lock pin groove 124 to venting volume 112 within valve spool bore 106, thereby providing fluid communication between spool annular lock pin groove 124 and venting volume 112.

Valve spool 30 also includes a spool advance passage 130 which extends radially inward from the outer periphery of valve spool 30 to phasing volume 110 within valve spool bore 106 in order to provide fluid communication between the outer periphery of valve spool 30 and phasing volume 110.

Valve spool 30 also includes a spool recirculation passage 134 which extends radially inward from the outer periphery of valve spool 30 to phasing volume 110 within valve spool bore 106. Phasing check valve 62 is located in phasing volume 110 in order to allow oil to enter phasing volume 110 from spool recirculation passage 134 while substantially preventing oil from exiting phasing volume 110 to spool recirculation passage 134. Spool recirculation passage 134 is spaced axially from spool advance passage 130 such that spool advance passage 130 is located axially between spool recirculation passage 134 and lock pin land 122.

Valve spool 30 also includes a spool retard passage 142 which extends radially inward from the outer periphery of valve spool 30 to phasing volume 110 within valve spool bore 106 in order to provide fluid communication between the outer periphery of valve spool 30 and phasing volume 110. Spool retard passage 142 is spaced axially from spool advance passage 130 such that spool recirculation passage 134 is axially between spool retard passage 142 and spool advance passage 130.

Valve spool 30 also includes a first vent passage 144 which extends radially inward from the outer periphery of valve spool 30 to venting volume 112 within valve spool bore 106 in order to provide fluid communication between the outer periphery of valve spool 30 and venting volume 112.

It should be noted that the portion of valve spool 30 which includes spool advance passage 130, spool recirculation passage 134, spool retard passage 142, and first vent passage 144 is sized to fit within valve bore 64 in a close sliding relationship such that oil is substantially prevented from communicating between spool advance passage 130, spool recirculation passage 134, spool retard passage 142, and first vent passage 144 along the interface of valve spool 30 and valve bore 64.

Valve spool 30 also includes second vent passages 146 which extend radially outward from venting volume 112, thereby allowing oil within venting volume 112 to be vented to valve bore 64 and out of camshaft phaser 12 where it may be drained back to oil source 76. Alternatively, a passage could be formed in camshaft phaser attachment bolt 28 which extends from valve bore 64 to a drain passage in camshaft 14 in order to vent oil within venting volume 112 where it may be drained back to oil source 76.

Actuator 102 may be a solenoid actuator that is selectively energized with an electric current of varying magnitude in order to position valve spool 30 within valve bore 64 at desired axial positions, thereby controlling oil flow to achieve desired operation of camshaft phaser 12. In a default position, when no electric current is supplied to actuator 102 as shown in FIG. 5, valve spring 104 urges valve spool 30 in a direction toward actuator 102 until valve spool 30 axially abuts a first stop member 148, which may be, by way of non-limiting example only, a snap ring within a snap ring groove extending radially outward from valve bore 64. In the default position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing oil to be supplied to phasing volume 110 from oil source 76. Also in the default position, lock pin land 122 is positioned to align spool annular lock pin groove 124 with bolt lock pin passages 86, thereby allowing oil to be vented from lock pin bore 66 via rotor lock pin passage 72, rotor annular lock pin groove 88, bolt lock pin passages 86, spool annular lock pin groove 124, spool lock pin passage 126, venting volume 112, and second vent passages 146 and consequently allowing lock pin spring 70 to urge lock pin 26 toward front cover 24. In the default position, lock pin land 122 also blocks fluid communication between bolt lock pin passages 86 and phasing volume 110. Also in the default position, spool advance passage 130 is positioned to permit fluid communication between bolt advance passages 92 and phasing volume 110 while first vent passage 144 is positioned to permit fluid communication between bolt retard passages 98 and venting volume 112. While spool retard passage 142 is aligned with spool recirculation passage 134, flow from phasing volume 110 to bolt retard passages 98 and to first vent passage 144 is prevented by phasing check valve 62. In this way, oil is vented from retard chambers 44 and oil from oil source 76 expands advance chambers 42 thereby causing a retard in timing of camshaft 14 relative to the crankshaft, and when lock pin 26 is aligned with lock pin seat 68, lock pin spring 70 urges lock pin 26 into lock pin seat 68 to retain rotor 20 in the predetermined aligned position with stator 18. However, it is important to note that oil can also flow from retard chambers 44 to advance chambers 42 through phasing check valve 62 depending on the pressure generated in retard chambers 44 due to torque reversals of camshaft 14.

In a first retard position, when an electric current of a first magnitude is supplied to actuator 102 as shown in FIG. 6, actuator 102 urges valve spool 30 in a direction toward valve spring 104 thereby causing valve spring 104 to be compressed slightly. In the first retard position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing pressurized oil to be supplied to phasing volume 110 through supply check valve 120 from oil source 76 when pressure within phasing volume 110 is lower than the pressure of oil source 76. Also in the retard position, lock pin land 122 is positioned to prevent fluid communication between bolt lock pin passages 86 and spool annular lock pin groove 124, thereby preventing oil from being vented from lock pin bore 66. In the first retard position, lock pin land 122 also opens fluid communication between bolt lock pin passages 86 and phasing volume 110, thereby allowing pressurized oil to be supplied to lock pin bore 66, and as a result, lock pin 26 compresses lock pin spring 70 and lock pin 26 is retracted from lock pin seat 68. It should be noted that by supplying oil to lock pin bore 66 from phasing volume 110, a separate dedicated supply for retracting lock pin 26 from lock pin seat 68 is not required. Also in the first retard position, spool advance passage 130 is positioned to permit fluid communication between bolt advance passages 92 and phasing volume 110 while first vent passage 144 is positioned to permit fluid communication between bolt retard passages 98 and venting volume 112. While spool retard passage 142 is aligned with spool recirculation passage 134, flow from phasing volume 110 to bolt retard passages 98 and to first vent passage 144 is prevented by phasing check valve 62. In this way, oil is vented from retard chambers 44 and oil from oil source 76 expands advance chambers 42 thereby causing a retard in timing of camshaft 14 relative to the crankshaft. However, it is important to note that oil can also flow from retard chambers 44 to advance chambers 42 through phasing check valve 62 depending on the pressure generated in retard chambers 44 due to torque reversals of camshaft 14.

In a second retard position, when an electric current of a second magnitude is supplied to actuator 102 as shown in FIG. 7, actuator 102 urges valve spool 30 in a direction toward valve spring 104 slightly more than in the first retard position, thereby causing valve spring 104 to be compressed slightly further. In the second retard position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing pressurized oil to be supplied to phasing volume 110 through supply check valve 120 from oil source 76 when pressure within phasing volume 110 is lower than the pressure of oil source 76. Also in the second retard position, lock pin land 122 is positioned to prevent fluid communication between bolt lock pin passages 86 and spool annular lock pin groove 124, thereby preventing oil from being vented from lock pin bore 66. In the second retard position, lock pin land 122 also opens fluid communication between bolt lock pin passages 86 and phasing volume 110, thereby allowing pressurized oil to be supplied to lock pin bore 66, and as a result, lock pin 26 compresses lock pin spring 70 and lock pin 26 is retracted from lock pin seat 68. Also in the second retard position, spool advance passage 130 is positioned to permit fluid communication between bolt advance passages 92 and phasing volume 110 while first vent passage 144 is positioned to prevent fluid communication between bolt advance passages 92 venting volume 112 and also prevent fluid communication between bolt retard passages 98 and venting volume 112. Also in the retard position, spool advance passage 130 is positioned to permit fluid communication between bolt advance passages 92 and phasing volume 110 while spool retard passage 142 is positioned to permit fluid communication between bolt retard passages 98 and phasing volume 110 via spool recirculation passage 134 and phasing check valve 62. In this way, torque reversals of camshaft 14 that tend to pressurize oil within retard chambers 44 cause oil to be vented out of retard chambers 44 and to be supplied to advance chambers 42. However, torque reversals of camshaft 14 that tend to pressurize oil within advance chambers 42 are prevented from venting oil from advance chambers 42 because phasing check valve 62 prevents oil from being supplied to retard chambers 44. Consequently, in the second retard position, torque reversals of camshaft 14 cause rotor 20 to rotate relative to stator 18 to cause a retard in timing of camshaft 14 relative to the crankshaft. It should be noted that supply check valve 120 prevents oil from being communicated to oil source 76 from phasing volume 110 when torque reversals of camshaft 14 produce oil pressures that are greater than the pressure produced by oil source 76. It should also be noted that since first vent passage 144 is positioned to prevent fluid communication between bolt advance passages 92 venting volume 112 and also prevent fluid communication between bolt retard passages 98 and venting volume 112, it is the pressure generated by the torque reversals alone that cause a change in phase relationship, i.e. the pressurized oil from oil source 76 does not contribute to the change in phase relationship other than replacing oil that may have leaked from camshaft phaser 12.

In a hold position, when an electric current of a third magnitude is supplied to actuator 102 as shown in FIG. 8, actuator 102 urges valve spool 30 in a direction toward valve spring 104 thereby causing valve spring 104 to be compressed slightly more than in the second retard position. In the hold position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing pressurized oil to be supplied to phasing volume 110 through supply check valve 120 from oil source 76 when pressure within phasing volume 110 is lower than the pressure of oil source 76. Also in the hold position, lock pin land 122 is positioned to prevent fluid communication between bolt lock pin passages 86 and spool annular lock pin groove 124, thereby preventing oil from being vented from lock pin bore 66. In the hold position, lock pin land 122 also opens fluid communication between bolt lock pin passages 86 and phasing volume 110, thereby allowing pressurized oil to be supplied to lock pin bore 66, and as a result, lock pin 26 compresses lock pin spring 70 and lock pin 26 is retracted from lock pin seat 68. Also in the hold position, spool advance passage 130 is positioned to block fluid communication between bolt advance passages 92 spool advance passage 130. Similarly, in the hold position, spool retard passage 142 is positioned to block fluid communication between bolt retard passages 98 and spool retard passage 142. Consequently, the rotational position of rotor 20 relative to stator 18 is substantially maintained in the hold position.

In a first advance position, when an electric current of a fourth magnitude is supplied to actuator 102 as shown in FIG. 9, actuator 102 urges valve spool 30 in a direction toward valve spring 104 thereby causing valve spring 104 to be compressed slightly more than in the hold position. In the first advance position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing pressurized oil to be supplied to phasing volume 110 through supply check valve 120 from oil source 76 when pressure within phasing volume 110 is lower than the pressure of oil source 76. Also in the first advance position, lock pin land 122 is positioned to prevent fluid communication between bolt lock pin passages 86 and spool annular lock pin groove 124, thereby preventing oil from being vented from lock pin bore 66. In the first advance position, lock pin land 122 also opens fluid communication between bolt lock pin passages 86 and phasing volume 110, thereby allowing pressurized oil to be supplied to lock pin bore 66, and as a result, lock pin 26 compresses lock pin spring 70 and lock pin 26 is retracted from lock pin seat 68. Also in the first advance position, spool retard passage 142 is positioned to permit fluid communication between bolt retard passages 98 and phasing volume 110 while first vent passage 144 is positioned to prevent fluid communication between bolt advance passages 92 and venting volume 112 and also prevent fluid communication between bolt retard passages 98 and venting volume 112. Also in the first advance position, spool retard passage 142 is positioned to permit fluid communication between bolt retard passages 98 and phasing volume 110 while spool advance passage 130 is positioned to permit fluid communication between bolt advance passages 92 and phasing volume 110 via spool recirculation passage 134 and phasing check valve 62. In this way, torque reversals of camshaft 14 that tend to pressurize oil within advance chambers 42 cause oil to be vented out of advance chambers 42 and to be supplied to retard chambers 44. However, torque reversals of camshaft 14 that tend to pressurize oil within retard chambers 44 are prevented from venting oil from retard chambers 44 because phasing check valve 62 prevents oil from being supplied to advance chambers 42. Consequently, in the first advance position, torque reversals of camshaft 14 cause rotor 20 to rotate relative to stator 18 to cause a retard in timing of camshaft 14 relative to the crankshaft. It should be noted that supply check valve 120 prevents oil from being communicated to oil source 76 from phasing volume 110 when torque reversals of camshaft 14 produce oil pressures that are greater than the pressure produced by oil source 76. It should also be noted that since first vent passage 144 is positioned to prevent fluid communication between bolt advance passages 92 venting volume 112 and also prevent fluid communication between bolt retard passages 98 and venting volume 112, it is the pressure generated by the torque reversals alone that cause a change in phase relationship, i.e. the pressurized oil from oil source 76 does not contribute to the change in phase relationship other than replacing oil that may have leaked from camshaft phaser 12.

In a second advance position, when an electric current of a fifth magnitude is supplied to actuator 102 as shown in FIG. 10, actuator 102 urges valve spool 30 in a direction toward valve spring 104 thereby causing valve spring 104 to be compressed slightly more than in the first advance position until valve spool 30 abuts a second stop member 150, which may be, by way of non-limiting example only, a shoulder formed in valve bore 64. In the second advance position, supply land 114 is positioned to open bolt supply passages 74, thereby allowing pressurized oil to be supplied to phasing volume 110 through supply check valve 120 from oil source 76 when pressure within phasing volume 110 is lower than the pressure of oil source 76. Also in the second advance position, lock pin land 122 is positioned to prevent fluid communication between bolt lock pin passages 86 and spool annular lock pin groove 124, thereby preventing oil from being vented from lock pin bore 66. In the second advance position, lock pin land 122 also opens fluid communication between bolt lock pin passages 86 and phasing volume 110, thereby allowing pressurized oil to be supplied to lock pin bore 66, and as a result, lock pin 26 compresses lock pin spring 70 and lock pin 26 is retracted from lock pin seat 68. Also in the second advance position, spool retard passage 142 is positioned to permit fluid communication between bolt retard passages 98 and phasing volume 110 while first vent passage 144 is positioned to permit fluid communication between bolt advance passages 92 and venting volume 112. While spool advance passage 130 is aligned with spool recirculation passage 134, flow from phasing volume 110 to bolt advance passages 92 and to first vent passage 144 is prevented by phasing check valve 62. In this way, oil is vented from advance chambers 42 and oil from oil source 76 expands advance chambers 42 thereby causing an advance in timing of camshaft 14 relative to the crankshaft. However, it is important to note that oil can also flow from advance chambers 42 to retard chambers 44 through phasing check valve 62 depending on the pressure generated in advance chambers 42 due to torque reversals of camshaft 14.

In summary, first vent passage 144 selectively provides a path to vent either advance chambers 42 or retard chambers 44, thereby selectively allowing a combination of oil pressure from oil source 76 and torque reversals of camshaft 14 to cause a change in phase relationship between camshaft 14 and the crankshaft of internal combustion engine 10. However, when desired, first vent passage 144 can be blocked, thereby resulting in only torque reversals of camshaft 14 to cause a change in phase relationship between camshaft 14 and the crankshaft of internal combustion engine 10.

As shown in the figures, phasing check valve 62 and supply check valve 120 may each be simple one piece devices that are made of formed sheet metal that is resilient and compliant and captured between insert 108 and valve spool bore 106. While phasing check valve 62 and supply check valve 120 have been shown as being distinct elements, it should now be understood that phasing check valve 62 and supply check valve 120 may be made from a single piece of formed sheet metal such that phasing check valve 62 and supply check valve 120 share a common portion that engages insert 108. It should also now be understood that one or both of phasing check valve 62 and supply check valve 120 may take numerous other forms known in the art of check valves and may include multiple elements such as coil compression springs and balls.

Insert 108 will now be describe with additional reference to FIGS. 11-13 where FIGS. 11 and 12 are isometric views of insert 108 and FIG. 13 is an isometric axial cross-sectional view of valve spool 30 and insert 108. Insert 108 includes a pair of opposing insert sidewalls 152 which extend axially within valve spool bore 106. Insert sidewalls 152 are contoured to conform to valve spool bore 106 and are spaced apart to allow insert sidewalls 152 to sealingly engage valve spool bore 106 to substantially prevent oil from passing between the interface of insert sidewalls 152 and valve spool bore 106. An insert dividing wall 154 traverses insert sidewalls 152 such that one side of insert dividing wall 154 is laterally offset from valve spool bore 106 and faces toward phasing volume 110 while the other side of insert dividing wall 154 is laterally offset from valve spool bore 106 and faces toward venting volume 112. A phasing check valve pocket 156 and a supply check valve pocket 158 may be defined within the side of insert dividing wall 154 that faces toward phasing volume 110 in order to receive portions of phasing check valve 62 and supply check valve 120 respectively, thereby positively positioning phasing check valve 62 and supply check valve 120 within phasing volume 110. One end of insert sidewalls 152 terminate at a circular insert base 160 which is received within a valve spool counter bore 162 of valve spool bore 106. An insert base end wall 164 is defined between insert base 160 and insert dividing wall 154 to close off one end of phasing volume 110 while an insert base passage 166 is defined between insert base 160 and insert dividing wall 154 to open venting volume 112 to the portion of valve bore 64 that contains valve spring 104 in order to provide a vent path for any oil that may leak thereinto. Insert base 160 may also serve as a spring seat to valve spring 104. An insert end wall 168 is defined at the other end of insert sidewalls 152 in order to close off the other end of phasing volume 110. It should be noted that insert end wall 168 keeps venting volume 112 open to second vent passages 146. A pair of insert retention members 170 may extend axially from insert end wall 168 to snap over and engage the end of valve spool 30 in order to axially retain insert 108 and also to radially orient insert 108 within valve spool bore 106. Alternatively, insert retention members 170 may be omitted because valve spring 104 may be sufficient to retain insert 108 within valve spool bore 106. In the case that insert retention members 170 are omitted, other features may be needed to radially orient insert 108 within valve spool bore 106.

While camshaft phaser 12 has been described as defaulting to full advance, it should now be understood that camshaft phaser 12 may alternatively default to full retard by simply rearranging oil passages. Similarly, while full advance has been described as full counterclockwise rotation of rotor 20 within stator 18 as shown in FIG. 2, it should also now be understood that full advance may alternatively be full clockwise rotation of rotor 20 within stator 18 depending on whether camshaft phaser 12 is mounted to the front of internal combustion engine 10 (shown in the figures) or to the rear of internal combustion engine 10.

While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow. 

We claim:
 1. A camshaft phaser for use with an internal combustion engine for controllably varying the phase relationship between a crankshaft and a camshaft in said internal combustion engine, said camshaft phaser comprising: an input member connectable to said crankshaft of said internal combustion engine to provide a fixed ratio of rotation between said input member and said crankshaft; an output member connectable to said camshaft of said internal combustion engine and defining an advance chamber and a retard chamber with said input member; a supply passage which introduces pressurized oil into said camshaft phaser from an oil source; a vent passage which selectively discharges oil from said camshaft phaser; and a valve spool within said output member which is moveable between a first position and a second position; wherein said first position 1) prevents fluid communication between said advance chamber and said vent passage, 2) prevents fluid communication between said retard chamber and said vent passage, 3) allows oil to flow from one of said advance chamber and said retard chamber to the other of said advance chamber and said retard chamber, and 4) prevents oil flow from the other of said advance chamber and said retard chamber to said one of said advance chamber and said retard chamber; wherein said second position 1) provides fluid communication between said vent passage and one of said advance chamber and said retard chamber, 2) prevents fluid communication between said vent passage and the other of said advance chamber and said retard chamber, and 3) provides fluid communication between said supply passage and the other of said advance chamber and said retard chamber.
 2. A camshaft phaser as in claim 1, wherein: said first position allows oil to flow from said retard chamber to said advance chamber and prevents oil flow from said advance chamber to said retard chamber; said second position 1) provides fluid communication between said vent passage and said retard chamber, 2) prevents fluid communication between said vent passage and said advance chamber, and 3) provides fluid communication between said supply passage and said advance chamber; and said valve spool is also moveable to a third position which 1) prevents fluid communication between said advance chamber and said vent passage, 2) prevents fluid communication between said retard chamber and said vent passage, 3) allows oil to flow from said advance chamber to said retard chamber, and 4) prevents oil flow from said retard chamber to said advance chamber.
 3. A camshaft phaser as in claim 2, wherein said valve spool is also moveable to a fourth position which 1) provides fluid communication between said vent passage and said advance chamber, 2) prevents fluid communication between said vent passage and said retard chamber, and 3) provides fluid communication between said supply passage and said retard chamber.
 4. A camshaft phaser as in claim 3, wherein said valve spool is also moveable to a fifth position which 1) prevents fluid communication between said advance chamber and said vent passage, 2) prevents fluid communication between said retard chamber and said vent passage, 3) prevents oil flow from said advance chamber to said retard chamber, and 4) prevents oil flow from said retard chamber to said advance chamber.
 5. A camshaft phaser as in claim 4, wherein: said valve spool moves along an axis between said first position, said second position, said third position, said fourth position, and said fifth position; and said fifth position is axially between said first position and said third position.
 6. A camshaft phaser as in claim 5, wherein: said first position is axially between said second position and said fifth position; and said third position is axially between said fourth position and said fifth position.
 7. A camshaft phaser as in claim 1, wherein: said valve spool includes a valve spool bore which includes a phasing volume and a venting volume within said valve spool bore such that said phasing volume is fluidly segregated from said venting volume; said valve spool includes a valve spool vent passage in constant fluid communication with said venting volume; said valve spool vent passage provides fluid communication from said one of said advance chamber and said retard chamber to said venting volume when said valve spool is in said second position; fluid communication from said one of said advance chamber and said retard chamber to said venting volume is prevented when said valve spool is in said first position; said said phasing volume receives pressurized oil from said supply passage.
 8. A camshaft phaser as in claim 7, wherein fluid communication from the other of said advance chamber and said retard chamber to said venting volume is prevented when said valve spool is in said first position and when said valve spool is in said second position.
 9. A camshaft phaser as in claim 7, wherein: said first position allows oil to flow from said retard chamber to said advance chamber and prevents oil flow from said advance chamber to said retard chamber; said second position 1) provides fluid communication between said vent passage and said retard chamber through said valve spool vent passage, 2) prevents fluid communication between said vent passage and said advance chamber, and 3) provides fluid communication between said supply passage and said advance chamber; and said valve spool is also moveable to a third position which 1) prevents fluid communication between said retard chamber and said vent passage, 2) prevents fluid communication between said advance chamber and said vent passage, 3) allows oil to flow from said advance chamber to said retard chamber, and 4) prevents oil flow from said retard chamber to said advance chamber.
 10. A camshaft phaser as in claim 9, wherein said valve spool is also moveable to a fourth position which 1) provides fluid communication between said vent passage and said advance chamber through said valve spool vent passage, 2) prevents fluid communication between said vent passage and said retard chamber, and 3) provides fluid communication between said supply passage and said retard chamber.
 11. A camshaft phaser as in claim 10, wherein: fluid communication from said advance chamber to said venting volume through said valve spool vent passage is prevented when said valve spool is in said first position, in said second position, and in said third position; and fluid communication from said retard chamber to said venting volume through said valve spool vent passage is prevented when said valve spool is in said first position, in said third position, and in said fourth position.
 12. A camshaft phaser as in claim 10, wherein said valve spool is also moveable to a fifth position which 1) prevents fluid communication between said advance chamber and said vent passage, 2) prevents fluid communication between said retard chamber and said vent passage, 3) prevents oil flow from said advance chamber to said retard chamber, and 4 prevents oil flow from said retard chamber to said advance chamber.
 13. A camshaft phaser as in claim 12, wherein: fluid communication from said advance chamber to said venting volume through said valve spool vent passage is prevented when said valve spool is in said first position, in said second position, in said third position, and in said fifth position; and fluid communication from said retard chamber to said venting volume through said valve spool vent passage is prevented when said valve spool is in said first position, in said third position, in said fourth position, and in said fifth position.
 14. A camshaft phaser as in claim 7, wherein: fluid communication is provided from said phasing volume to the other of said advance chamber and said retard chamber when said valve spool is in said first position and also when said valve spool is in said second position; and oil flow is prevented from said phasing volume to said one of said advance chamber and said retard chamber when said valve spool is in said first position and also when said valve spool is in said second position.
 15. A camshaft phaser as in claim 7, wherein; said valve spool moves along an axis between said first position and said second position; and said valve spool vent passage extends from an outer periphery of said valve spool to said venting volume in a direction toward said axis. 